How Does High-Performance Alloy Tool Steel Work?

Advantages of High-Speed Steel

The use of HSS in industrial and manufacturing processes offers a range of benefits, which include the following:

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AdvantageDescriptionGrindabilityThe ability to be shaped and sharpened easily without losing structural integrity makes HSS ideal for creating and maintaining complex tool geometries.StrengthHSS’s composition gives it exceptional strength, allowing tools to resist breaking or chipping under heavy loads or impact conditions.Temperature ResistanceHSS retains its hardness at high temperatures, which is critical for maintaining performance during rapid cutting operations.Cost-EffectivenessWhen compared to materials like carbides, HSS tools are less expensive to produce, making them more accessible for a variety of applications.Enhanced PerformanceThe application of modern coatings can extend the life of HSS tools and increase their efficiency, allowing for faster cutting speeds and longer intervals between sharpening.

The combination of these advantages makes high-speed steel a versatile and valuable material in the tool-making industry. Its ability to withstand the rigors of high-speed machining and maintain a sharp edge while being relatively inexpensive to produce, ensures its continued use in a variety of applications, from the workshop floor to high-end precision manufacturing.

Applications of High-Speed Steel

HSS is a category of tool steel that is prized for its ability to cut material at high speeds. Here are some detailed applications:

1. Manufacture of Cutting Tools: 
   • Drills: HSS is commonly used to make drill bits and tool bits due to its hardness and durability.
   • Turning Tools: These are used in lathes for cutting metals, and HSS is preferred for its toughness.
   • Milling Tools: HSS is used for end mills, gear cutters and other milling cutters due to its wear resistance.
2. Complex Tool Shapes: 
   • Profile Tools: The grindability of HSS makes it ideal for tools requiring precise and complex shapes.
3. Wood Processing Tools: 
   • Although cold work steel is traditionally used for woodcutting tools, HSS is sometimes selected for its superior performance in high-speed applications.

HSS has become the material of choice in many cutting applications, outperforming older materials like cold work steel, which is now relegated to less demanding tasks such as making files and rasps.

Microstructure of high-speed steel

The microstructure of high-speed steel is designed for optimum performance during machining. Quenching and tempering gives HSS a martensitic matrix that provides exceptional wear resistance and hardness. The addition of alloying elements such as tungsten, molybdenum and vanadium leads to the formation of hard carbides, which increases the strength and temperature resistance of the steel.

The unique microstructure of HSS enables hardness to be maintained at the high temperatures that occur during cutting processes. The carbides that form from the carbon and alloying elements are critical to the durability of HSS tools and enable them to withstand the harsh conditions at high cutting speeds.

Alloying elements

Like all steel, HSS also contains carbon. However, it also contains a number of other alloying elements, with tungsten and molybdenum playing the most important role.

Tungsten

Tungsten is crucial for the formation of carbides, in this case, tungsten carbide in particular. It increases the hot hardness, tempering resistance, wear resistance and thus improves the cutting ability of HSS. It also improves toughness.

Molybdenum

Molybdenum is a strong carbide former. It also enhances the same properties as tungsten. HSS grades with a high molybdenum content are subjected to complex heat treatment. It also ensures increased corrosion resistance.

Vanadium

Vanadium has a high hardness. The formation of vanadium carbide in the workpiece increases wear resistance, edge retention and heat resistance.

Chromium

The hardenability of steel is improved by the use of chromium. Chromium is also involved in the formation of carbides, which also increase wear resistance, edge retention and high-temperature strength.

Cobalt

Cobalt does not form carbides. However, it is alloyed to inhibit grain growth at elevated temperatures. It improves tempering resistance and high-temperature strength.

For more information, please visit High-Performance Alloy Tool Steel.

Carbon

Carbon is used to form carbides and for hardenability.

Maximize the Potential of High-Speed Steel with Bortec Group’s Advanced Treatments

In the realm of high-speed steel tools, performance and longevity are paramount. Bortec Group’s specialized treatments are designed to enhance these attributes, ensuring your tools operate at peak efficiency and durability. Discover how our services can transform your HSS tools:

• Boronizing with BOROCOAT®: Achieve unparalleled hardness and exceptional wear resistance for your HSS tools. Our boronizing service is perfect for applications demanding extreme durability, from valve construction to power plant technology. 
• Stainless Steel Hardening with BORINOX®: Elevate the performance of your stainless steel components. The BORINOX® process significantly enhances wear protection, maintaining uniform hardness even with complex geometries. 
• Nickel Plating with NICKELCOAT®: Protect your tools against corrosion and wear with our nickel plating service. NICKELCOAT® offers superior corrosion resistance, making it ideal for highly acidic environments and ensuring consistent coverage on intricate parts. 
• Nitriding for Steel and Cast Iron: For a hard, wear-resistant surface that stands up to abrasion and fatigue, consider our nitriding service. Our innovative process ensures no soft spots, providing a reliable and environmentally friendly solution for enhancing your HSS tools. 

Don’t let the extreme conditions of high-speed applications shorten the life of your tools. Contact Bortec Group today to learn more about how our advanced surface treatments can benefit your operations and give you the competitive edge you need.

Overcoming difficulties in the metallographic preparation of high alloy tool steels

Avoiding thermal damage
As heat treatability of high alloy tool steels is a quality criterion, thermal influence during cutting has to be avoided in order to ensure a true representation of the actual microstructure. When cutting larger sections, this preparation step has to be carried out with great care.

Fig. 2: Thermal damage due to faulty cutting conditions 

Preserving carbides and inclusions
The main difficulty during grinding and polishing of high alloy tool steels is ensuring that carbides and non-metallic inclusions are retained. In cold working tool steels, the primary carbides are very large and fracture easily during grinding. In fully annealed conditions, secondary carbides are very fine and can easily be pulled out from the softer matrix.

Fig. 3: Fractured primary carbides (Mag: 200x) 

Large volume processing of high alloy tool steels
For quality control teams working within high alloy tool steel production, processing large sample volumes requires a very efficient organization of the workflow, automatic equipment and standard procedures.

Recommendations for the grinding and polishing of high alloy tool steel

When preparing high alloy tool steels for metallographic analysis, the form, size and amount of carbides must be accurately represented. In addition, non-metallic inclusions must be retained in an undeformed matrix.

• Large volumes are best processed on fully automatic grinding and polishing machines, which guarantee a fast and efficient workflow and reproducible results.
• Tool steels are hard. Therefore, fine grinding with diamond is more efficient and economical than grinding with silicon carbide foil.
• Sometimes a final oxide polish can be useful for contrasting and identifying carbides.

Table 1: Preparation method for high alloy tool steel on large automatic equipment.
DiaPro diamond suspensions can be substituted with DP-Diamond suspension P as follows: For FG with 9 μm, DP 2 with 1 μm used with DP-Blue/Green lubricant. 

Table 2: Preparation method for high alloy tool steel on table-top semi-automatic equipment.
DiaPro diamond suspensions can be substituted with DP-Diamond suspension P as follows: For FG with 9 μm, DP 1 with 3 μm, DP 2 with 1 μm used with DP-Blue/Green lubricant.

Find out more

• Get more knowledge, expertise and insight in our grinding and polishing section.
• See our range of grinding and polishing machines and equipment.
• Get consumables and accessories for metallographic grinding and polishing.

Recommendations for the etching of high alloy tool steel

High alloy tool steel samples are usually initially examined unetched to identify inclusions and carbide size and formation. To reveal the microstructure, various concentrations of nital or picral are used.

For example, to show the carbide distribution in cold work steel, a 10% nital ensures the matrix is dark and the white primary carbides stand out. For fine globular pearlite, a brief submersion into picric acid followed by 2% nital gives a good contrast and avoids staining.

Nital etching solution:
100 ml ethanol
2-10 ml nitric acid (Caution: Do not exceed 10% of the solution as it becomes explosive!)

Picral etching solution:
100 ml ethanol
1-5 ml hydrochloric acid
1-4 g picric acid


Fig 5: Cold work tool steel etched with 10% nital, primary carbides stand out white

Fig. 6: Hot work tool steel etched with picral and nital, globular pearlite (Mag: 500x)

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